The present invention relates to substrate processing, and more particularly to a method and apparatus for improved substrate handling.
Cluster tools are commonly used in the fabrication of integrated circuits. A cluster tool typically includes a load lock chamber for introducing substrates (e.g., semiconductor wafers) into the tool and a central transfer chamber for moving substrates between the load lock chamber and a plurality of processing chambers and one or more cool down chambers mounted on the transfer chamber. Typically, either a single blade or a double blade robot is located within the transfer chamber to move substrates between the load lock chamber, the processing chambers, the cool down chamber(s) and then back to the load lock chamber. Exemplary cluster tools, robots and substrate handling methods are described in U.S. Pat. Nos. 4,951,601 and 5,292,393, both of which are incorporated herein by reference in their entirety.
Within a cluster tool a typical substrate handler arm capable of 360xc2x0 rotation and extension is positioned inside the central transfer chamber. In operation the substrate handler rotates to align its blade with a sealable slit (e.g., a slit valve) which connects the central transfer chamber to a load lock chamber (i.e., a load lock slit). The substrate handler extends through the load lock slit, picks up a substrate, retracts, swings the blade about a central axis to position the substrate in front of a processing chamber slit (which connects the central transfer chamber with the processing chamber) and extends through the slit to place the substrate in the processing chamber. After the processing chamber finishes processing the substrate, the wafer handler extends through the processing chamber slit, picks of the substrate, retracts and moves to position the substrate in front of a cool down chamber slit. The substrate handler again extends placing the substrate in the cool down chamber and then retracts therefrom. After substrate cooling is complete, the substrate handler extends through the cool down chamber slit, picks up the substrate and retracts through the cool down chamber slit in order to extract the substrate and carry the substrate to another processing chamber or return the substrate to the load lock chamber. While the substrate is processing or cooling, the substrate handler places and extracts other substrates from the remaining chambers (e.g., load lock, processing or cool down chambers) in the same manner. Thus, the substrate handler undergoes a complex pattern of rotations or arcs about the axis and extensions, requiring a mechanically complex and expensive substrate handler. Further, each substrate handler extension and arcuate motion requires considerable operating space and may introduce reliability problems.
One way to improve system efficiency is to provide a robot arm having the ability to handle two substrates at the same time. Thus, some equipment manufacturers have provided a robot arm in which two carrier blades are swung about a pivot point at the robot wrist (e.g., via a motor and belt drive positioned at the substrate handler""s wrist, or magnetic coupling between the robot shaft and a motor). Thus, a first substrate (e.g., to be processed) may be stored on one blade while the other blade picks up a second substrate (e.g., previously processed). The carrier blades are then repositioned and the first stored substrate is placed as desired. Such a mechanism is rather complex and requires a massive arm assembly to support the weight of a carrier blade drive located at the end of an extendible robot arm. For example, two drives are usually required for a system incorporating such a robot arm, whereby movement in opposite directions of the shafts extends or retracts the blade, and movement in the same direction swings the blade around the shafts"" centerline. Any improvement in throughput provided by such a multiple carrier robot comes at a price of increased equipment/manufacturing cost, increased weight and power consumption, and increased complexity and, thus, reduced reliability and serviceability.
Another approach places two separate robot arms coaxially about a common pivot point. Each such robot arm operates independently of the other and improved throughput can be obtained through the increased handling capacity of the system. However, it is not simple to provide two robot arms for independent operation about a common axis. Thus, multiple drives must be provided, again increasing manufacture/equipment costs and complexity while reducing reliability.
The various processes which are performed on the various substrates, may require different processing times. Therefore, some substrates may remain in a chamber for a short period of time after processing is completed before they are moved into a subsequent processing chamber because the subsequent processing chamber is still processing another substrate. This causes a substrate back log and decreases system throughput.
In addition to varying processing times, another factor which affects throughput is the need to cool individual substrates following processing. Specifically, the number of movements a substrate handler must make in order to process numerous substrates increases significantly when the substrates must be transferred to one or more cool down chambers following each processing step. Additionally, incorporation of one or more cool down chambers reduces the number of positions on the transfer chamber where a processing chamber may be positioned. Fewer processing chambers can result in lower system throughput and can increase the cost of each wafer processed.
Therefore, there remains a need for a method and apparatus for improved substrate handling module which can increase substrate throughput while preferably providing substrate cooling.
A transfer chamber for use in substrate process is provided. The transfer chamber contains a rotatable substrate carriage, and a temperature adjustment plate located in the upper portion of the chamber and a substrate handler located in a lower portion of the chamber. The substrate carriage is adapted so as to raise and lower between an elevation below an elevation of the substrate handler""s blade, and an elevation above the elevation of the substrate supporting surface of the temperature adjustment plate so as to place and extract substrates to and from the substrate handler""s blade and the temperature adjustment plate.
Other features and aspects of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawings.